1. Field of the Invention
This invention pertains to the field of polyurethane plastics. The invention more particularly relates to polymer polyols made from the reaction of polyester polyols with an organic polyisocyanate in the presence of a polyether polyol solvent.
2. Description of the Prior Art
The use of a polyol in the preparation of polyurethanes by reaction of the polyol with a polyisocyanate in the presence of a catalyst and perhaps other ingredients is well known. Conventional polyols for flexible polyurethane foams are usually made by the reaction of a polyhydric alcohol with an alkylene oxide, usually ethylene oxide and/or propylene oxide, to a molecular weight of about 2,000 to 3,000 and above. These polyols are then reacted with polyisocyanate in the presence of water or other blowing agents such as fluorocarbons to obtain polyurethane foams (see, for example, U.S. Pat. No. 2,929,800).
One technique of trying to improve the ultimate polyurethane foam or elastomer is to provide a polyol which is a dispersion of a polymer within a polyol solvent. The polymer may be the reaction product of another, different kind of polyol with a polyisocyanate or may be an unrelated polymer, such as the product in the co-polymerization of styrene and acrylonitrile.
U.S. Pat. No. 3,325,421 discloses a method of making a stable dispersion of a urea in a composition, where the dispersed phase is the reaction product of an organic polyisocyanate and a diamine having at least two reactive hydrogen atoms. The equilibrium product of two polyols, of which at least one is a polyester polyol, may be formed by heating them in the presence of a catalyst according to U.S. Pat. No. 3,666,724. The resulting co-polymer apparently gives better foams and elastomers.
Stable dispersions of polyureas can be prepared from mixtures consisting of hydroxyl-group containing materials, polyamines and polyisocyanates as taught by U.S. Pat. No. 4,089,835. The dispersing media may be a polyether, a polyester, a polyester amide or a polycarbonate, while the polyamine should contain primary or secondary amine groups.
British Pat. No. 2,098,229 discloses that polymer polyols for use in flexible foams may be made by reacting triethanolamine with a polyisocyanate in the presence of a polyol solvent. Polyurea polymer polyols made by the reaction of alkanolamines with polyisocyanates in the presence of polyether polyols and absence of a catalyst, may be stabilized by quenching with a secondary amine as described in U.S. Pat. No. 4,293,470.
A method for the preparation of stable dispersions of polyisocyanate polyaddition products by reacting organic polyisocyanates with compounds having primary and/or secondary amine groups or primary hydroxyl groups in polyols is taught by U.S. Pat. No. 4,093,569. The reaction is carried out in the presence of 4 wt.% water.
Other disclosures concerning the reaction of alkanolamines with polyisocyanates in a polyol solvent are U.S. Pat. Nos. 4,374,209 and 4,296,213. Polyester polymer polyols made by the reaction of a polyester polycarbonate, a polyether polyol and an organic polyisocyanate is described in U.S. Pat. No. 4,435,527.